Island biogeography of the Macaronesian Gesnouinia and Mediterranean Soleirolia (Parietarieae, Urticaceae) with implications for the evolution of insular woodiness

Abstract

Urticaceae tribe Parietarieae serves as an excellent example to study hypotheses on Macaronesian‐​Mediterranean island biogeography. Parietarieae is distributed in both of these floristically closely related regions and contains two island endemic genera. Gesnouinia is endemic to Macaronesia and was considered a Tertiary relict from a European paleotropical vegetation. This, however, may contradict the general idea of insular woodiness also proposed for this genus. For the origin of the western Mediterranean island endemic Soleirolia, a vicariance scenario, i.e., the split of the Hercynian massif in southern Europe has been suggested. To evaluate these hypotheses and to provide a time frame for island and inter‐island colonization, we applied molecular phylogenetics and dating based on two plastid and one nuclear DNA marker. Additionally, we performed ancestral area reconstruction, analyzed the anatomy of the stem and reconstructed the ancestral character states of woodiness. Our results indicate that Gesnouinia colonized Macaronesia during the Miocene via long‐distance dispersal and may, therefore, be a Tertiary laurel forest relict. Diversification between the laurel forest species Gesnouinia arborea and the rupicolous and more xeric G. filamentosa occurred within Macaronesia during the Pleistocene, possibly due to climate fluctuations. Therefore, G. arborea is not a relict from the Tertiary. Stem anatomy suggests that although woodiness in Gesnouinia likely is derived, it may have evolved prior to island colonization. Soleirolia originated in the Mediterranean during the Miocene. This rules out vicariance from the split of the Hercynian massif in southern Europe during the Oligocene. The divergence of Soleirolia from Majorca, Corsica, Sardinia and the Italian mainland dates to the Pleistocene. This indicates long‐distance dispersal as predominant colonization mode, not ruling out that migration between these areas was possibly facilitated by land bridges during the Pleistocene glaciation cycles.

Iconic, threatened, but largely unknown: Biogeography of the Macaronesian dragon trees (Dracaena spp.) as inferred from plastid DNA markers

“…Such an estimate agrees well with the discovery of fossil dragon tree imprints dating back to the late Pliocene (Marrero, ). Under the temporal framework depicted by fossil and molecular data, it is quite probable that, following successful dispersal, the islands provided Dracaena with habitat suitability throughout episodes of widespread extinction, such as those derived from Quaternary climatic oscillations (reviewed in García‐Verdugo & al., ; see also Schüßler & al., ).…”

Polyploidy on Islands: Its Emergence and Importance for Diversification

“…Indeed, nearby mainland Europe or Africa seems to be the ancestral areas for most Canary Island genera and species ( Sanmartín et al, 2008 ). This diversity and the ease to access the island system explains why the Canary Islands have become such an important natural laboratory for evolutionary botanists with studies investigating patterns of dispersal and evolution on the archipelago, such as the evolution of woodiness ( Böhle et al, 1996 ; Schüßler et al, 2019 ), breeding system ( Soto-Trejo et al, 2013 ), and photosynthetic pathways ( Mort et al, 2007 ). Most important in our context is the intensive karyological study of the archipelago (e.g., Suda et al, 2005 ; Table 1 ).…”

Are Cenozoic relict species also climatic relicts? Insights from the macroecological evolution of the giant sedges ofCarexsect.Rhynchocystis(Cyperaceae)

“…(Liu and Schneider, 2013), Visnea mocanera L.f., and Geranium L. (Schüßler, 2020). By contrast, Kondraskov et al (2015) proposed that MLFs could be a heterogeneous assembly composed of species of more recent origin, resulting from migration and colonization from different source areas during the Pleistocene (Vargas, 2007; Schüßler et al, 2019).…”